Mostly it changes the version number.

Linus Torvalds wrote in the Linux 6.19 release announcement:

"I have more than three dozen pull requests for when the merge window opens tomorrow - thank you to all the early maintainers. And as people have mostly figured out, I'm getting to the point where I'm being confused by large numbers (almost running out of fingers and toes again), so the next kernel is going to be called 7.0."